Iron powder core



Sept. 25, 1945. K, KASCHKE 2,385,578

IRON POWDER CORE Fil'ed Jan. 27. 1942 Patented Sept. 25, 1945 NETE IRON POWDER CORE I Kurt Kasohke, Berlin-Neukolln, Germany; vested in the Alien Property Custodian Application January 27, i942, sei-ni No. 428,442

1n Germanyluly 20, 1940 3 Claims.

a great inductance variation, windings of considerable length have been used with oblong pencillike cores arranged to be moved within the winding. The production of iron dust cores of such pencil-like shape has involved considerable dimculties since the cores are required to combine low losses and high permeability. In many lnstarlces cores are required having a permeability above 30 corresponding to a specific density of over 6. 4The conventionalprocess of compressing the iron powder mixiture in a tubular hollow mould by means of a piston sliding in said mould did not give satisfactory results. Owing to the' high friction at the walls of themouldthe pressure could not be evenly distributed throughout the `core structure and the central portion of the core proved to be insufciently compressed. Moreover, the insulation of the magnetic particles at the surface of the core is liable to injury owing to the friction exerted upon the core surface as the same is ejected from the mould, producing a conductive metal skin which tends to increase the losses in the iron core.

According to the present invention iron dust 'cores of the type above referred to are made in the form of symmetrical halves which are divided in an axial direction of the core and subsequently united to form a round rod shaped iron core. The core halvesare compressed in a direction -perpendicularly to the axis of the core and then connected together. preferably with the aid of an adhesive. This method oiers the advantage that the cores can be made on automatically operating machines, and can be readily removed from the mould withoutany danger of injury to the insulation at the surface of the cores. Moreover, the cores can be made with a very uniform structure and, if desired, holes or other recesses of any shape can be provided in the cores. For example, conical bores eral fiat faces of tapered or otherl shape can be provided such as are required. for instance, in

or undercut bores or threaded bores can be produced. Further, lat- (ci. 11s-21) order to produce inductance changes of a predetermined characteristic.

The invention will be better understood by reference to the following detailed description in connection with the accompanying drawing showing by way of example and purely schematically some embodiments of the invention and in which Fig. 1 is a perspective view of two core halves constituting the elements of a core in accordance with the invention. y

Figs. 2, 3 and-4 are modified core halves including central recesses.

Fig. 5 is a central section of a permeability tuning device including a c ore made in accordance with the presentdnvention.

A Fig. 6 is an axial section through a mould adapted for making cores in accordance with the present invention and Fig. 7 is. an axial section similar to Fig. 6, but showing the pants of the mould in another working position.

Referring now to the drawing in greater detail and first to Fig. 1, it will be noted that the oblongy core is made of two semi-cylindrical core halves i and 2 which may consist of any suitable mixture of magnetic powder and an insulating binder, with or without an individual insulating skin applied on each particle. It should lbe noted that the term iron powder or magnetic powder as used in this speciiication is intended to compriseany metal or other material whose permeability is greater than 1 and whose high frequency losses are so low that the material may be used in high frequency devices.

Referring to Figures 2, 3 and 4 it will be seen that-the core halves in this case are provided with recesses, i. e. the core of Fig. 2 is provided with a cylindrical bore Il, that of Fig. 3 is formed with a threaded bore .4, and the core of Fig. 4 is provided with a differential bore 5, the diameter of the inner portion of the bore being larger than that of the outer portion. In addition, the core of Fig. 2 is formed with a tapered outer surface 3, while the core of Fig. 4 is formed with a conical bore 6. The tapered surface 3 of Fig. 2 and the conical bore 8 of Fig. 4 serve to vary the eirective permeability of the core in such a manner that the effective permeability decreases towards one end of the core.

Fig. 5 illustrates a permeability comprising a core i8 which consists of two halves and is provided vwith a conical bore in accordance with Fig. 4 and with a hook 'l which may be seated in a bore similar to that indicated at l in tuning device Fig. 4, and a winding l having a relatively high ratio of length to diameter.

A very suitable method of making core halves according to the invention will now be described with reference to Figs. 6 and 7.

The pressing tool shown in these figures comprises a casing Il with hardened steel cheeks II making up the mould and a lower punch or piston I3. An upper punch I5 is formed with a semicircular projection Il to produce recesses like those indicated at I'I, 4 and 5 in Figs. v2, 3 and4 respectively.

This pressing tool operates as follows:

The space in mould is at first filled with'a suitable mixture of magnetic powder and a binder. Now the upper punch I5 is moved downwards to compact the powder into a semi-cylindrical shaped article IC. Following the compression punch I5 is retracted and the lower punch I3 is pushed upwards to eject the cheeks Il as indicated in Fig. 7, whereby the moulded part I6 is set tree and may be removed by hand without any injury to its surface. Punch I5 now returns to its initial position, allowing cheeks ii to assume their initial positions shown. in Fis. 6, and the whole cycle or operations may be repeated. A pair of such core halves may new be united, for instance, by gluelng there. together with the aid of an adhesive which may consist ora solvent adapted to dissolve the insulating binder contained in the core.`

My improved method may also be used for the production of hollow bodies and bodies of more complicated shape by compressing and sintering metal powder, which bodies may be used for various purposes such as bearing bushes.

I claim:

1. A compressed iron dust core for permeability timing devices whose length is amultiple of its diameter, said core comprising two substantially half-round portions glued together to i'crm a substantially round core body, said portions having recesses in their abutting faces forming cavities in the round core body, and said portionshaving an internal structure characteristic of a body formed by compression ci a finely divided material in a direction perpendicular to the longitudinal axis of the core.

2. A compressed iron core as dened in claim l in which the half-round portions have tapered 3. A compressed iron core as defined in claim 1 in which the half-round portions have tared 

